This invention relates to molds for injection forming of plastic parts, and in particular to a retainer for engaging a mold slide in a laterally offset position during opening of the mold and holding the slide until the mold is again reclosed.
In conventional molds for injection molding of plastic parts, in addition to the typical mating mold parts, one or more laterally moving slides is used to move one or more core parts as the mold is opened and closed. When such a slide is employed, typically the mold uses angled cam pins, known as angle pins, which are fixed to one of the mold parts and which pass through a corresponding bore in the slide. As the mold is opened, the angle of the angle pin "cams" the slide laterally outwardly to remove the core element from the molded piece. When the mold is closed, the procedure reverses, and the angle pin moves the slide toward the mold cavity to position the core element for molding of the next plastic piece.
In the operation of such molds, it is important that the slide be held in place when the mold is opened since, quite often, the mold parts are separated sufficiently so that the angle pin is completely withdrawn from its corresponding bore in the slide. Particularly in the case of molds having vertically-disposed slides, if the slide is not held by some other means, after the mold parts are fully separated, the slide can inadvertently become displaced, inhibiting closing of the mold without manual realignment of the slide. If such misalignment of the slide is not noticed, the mold itself can be damaged should an attempt be made to close the mold.
There has been various efforts to produce slide retainers to avoid alignment problems. For example, U.S. Pat. No. 3,811,645 discloses two types of retainers, a complex prior art retainer which is attached to the mold and juts outwardly from the mold body, and an internal slide retainer having a pin attached to either a mold part or the slide, and a corresponding pin retainer attached to the other of the mold part or the slide. When the mold is opened, the slide is displaced laterally and the pin engages the retainer to hold the slide in place until the mold is reclosed.
Although the retainers disclosed in U.S. Pat. No. 3,811,645 do, in fact, retain the slide in its laterally offset orientation, because of the parts involved, the retainers are complex, subject to failure, and costly in manufacture. Furthermore, for the internal slide disclosed in U.S. Pat. No. 3,811,645, the size of the retainer requires considerable modification of the mold to accommodate the retainer.